Linear data storage media refers to data storage media, such as magnetic tape, in which data is stored in parallel tracks that extend linearly along the length of the media. Examples of linear data storage media include magnetic tape, magneto-optic tape, optical tape, holographic tape, and possibly other tape-like media formats. Magnetic tape media remains an economical medium for storing large amounts of data. For example, magnetic tape cartridges, or large spools of magnetic tape are often used to back up large amounts of data for large computing centers. Magnetic tape cartridges also find application in the backup of data stored on smaller computers such as workstations, desktop or laptop computers.
In magnetic tape, data is typically stored as magnetic signals that are magnetically recorded on the medium surface. The data stored on the magnetic tape is often organized along data tracks, and read/write heads are positioned relative to the data tracks to write data to the tracks or to read data from the tracks. As the number of data tracks increases, the data storage capacity of the magnetic tape likewise increases. However, as the number of data tracks increases, the tracks become narrower and more crowded on the surface of the data storage tape.
Servo tracks or patterns refer to signals or other recorded marks on the magnetic tape and that are used for tracking purposes. In other words, servo patterns are recorded on magnetic tape to provide reference points for tracking the location of data tracks. Servo tracks can improve the ability to locate data tracks, particularly as the tracks become narrower and more crowded on the surface of the data storage tape. For example, a servo controller interprets detected servo tracks and generates position error signals that are used as feedback to adjust the lateral distance of read or write heads relative to the data tracks. Time-based servo patterns and amplitude-based servo patterns are common in magnetic tape.
A wide variety of heads have been designed to write data to magnetic tape. Various heads have also been designed to read data stored on magnetic tape. A magnetic data tape recording system often includes both write heads and read heads to facilitate the writing of information to the magnetic medium and readout of such information for verification that the data was written properly. Read-while-write sliders, for example, typically include a read head and a write head precisely mounted on a slider to facilitate readout and verification of data written by the write head.
Actuators refer to the elements that mechanically position a head with respect to a data storage medium, such as magnetic tape. For high density magnetic tape, actuators may be responsive to position error signals generated based on the readout of servo patterns recorded on the media surface. In some cases, a coarse positioning actuator can be used to position a head in general proximity to a desired location, and a fine positioning actuator can be used to precisely position the head in the desired location. The coarse positioning actuator may define a larger range of motion than the fine positioning actuator, but the fine positioning actuator has greater positioning accuracy.